1. Field of the Invention
This invention relates generally to an organic optoelectronic device and in particular to a structure for minimizing the effects of a defective organic optoelectronic device.
2. Description of the Related Art
Electronic devices such as passive matrix displays, alpha-numeric displays, detector arrays, or solar cell arrays include multiple organic optoelectronic devices (“elements”). These elements can be, for example, organic light emitting diodes (“OLEDs”) (the OLEDs can be used in, for example, displays or as the light source elements of a light source), light detectors, and solar cells.
In the electronic device, one of the major reasons for its failure is an electrical short occurring in one or more of the elements. A short occurs when any imperfection in the element structure causes its cathode to be in direct contact (or very close proximity) with its anode resulting in an area of much lower resistance than the remaining area between the anode and the cathode. Shorts may occur in any of the layers forming the element and may be caused by, for example, substrate imperfections or asperities, anode layer irregularities, non-uniformity of the one or more organic layers, and airborne particles introduced in the element structure during handling.
In the electronic device, a short may result in several types of cross-talk depending upon the manner in which the device is driven. As an example, FIG. 1 shows the effects of a shorted element on an electronic device. FIG. 1 shows a prior art passive matrix OLED display 100. Here, anodes of the OLED pixels are parallel strips of column electrodes, and cathodes of the OLED pixels are parallel strips of row electrodes. Each OLED pixel includes typically one or more organic layers and light is emitted from one of these layers. In order to produce a display image, for example, each row of cathodes is sequentially addressed and if any of the OLEDs within the addressed row are to be activated then the columns to which these OLEDs belong are set to a voltage “V”. For example, in FIG. 1, in order to address an OLED pixel 103 so that it doesn't emit light, cathode 1, cathode 2, and cathode 3 are set to voltage “V” and cathode 4 is set to zero voltage. Also, anode 3 is set to zero voltage. Since the OLED pixel 106 is not being addressed, it is reverse biased (i.e., its cathode is at a voltage “V” and its anode is at zero voltage). If the OLED pixel 106 is not shorted, then in reverse bias, no current or only a small amount of leakage current will flow across it. If, however, the OLED pixel 106 is shorted, then current will readily flow across it since the resistance is very low and thus the anode 3 will also be at the voltage “V” resulting in the OLED pixel 103 emitting light even though this OLED is not intended to emit light as shown by anode 3 being set to zero voltage. In the case that the OLED pixel 106 is shorted, since each cathode is addressed sequentially, all the OLEDs attached to anode 3 will emit light and a line at anode 3 will appear. Therefore, a short in a single OLED can result in cross-talk that makes it appear, for example, that the whole column is damaged. In this case, the shorted OLED causes a bright vertical line (i.e., a “ghost image”) to appear resulting in a lower display quality or even rendering the display unusable.
For the foregoing reasons, there exists a need to isolate an individual defective element so that there is a visible defect only at the defective element thus minimizing the effect of this defective element on the electronic device.